====== DHCP4-Dienst mit festen IPv4-Adressen ======
[[https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=717215|dhcpd/KVM Bug]] beachten (( Lösungsmöglichkeiten um UDP Checksum-Problem in KVM zu vermeiden: 
  * in KVM e1000 als Netzwerkkarte auswählen, 
  * oder: TX offloading in der Netzwerkkarte ausschalten
  * oder: mit iptables die Checksumme erzeugen
))
===== Pakete =====
Debian (ab 6.0):
  isc-dhcp-server

openSuSE (ab 12.1):
  dhcp-server

centos (6) :
  dhcp  

===== Konfiguration =====
''/etc/dhcp/dhcpd.conf'' : ( debian ab 6.0 )

''/etc/dhcpd.conf'' : ( openSuSE 12.1, centos 6 )
<file>
authoritative;
ddns-update-style none;

log-facility local7;

subnet 192.168.1.0 netmask 255.255.255.0 {
  option domain-name "linuxhotel.de";
  option routers 192.168.1.1;
  option broadcast-address 192.168.1.255;
  default-lease-time 600;
  max-lease-time 7200;
}

use-host-decl-names on;

host notebook24 {
  hardware ethernet 00:16:d3:b9:a0:3e;
  fixed-address 192.168.1.224;
}
</file>

=== Debian ab 6.0 ===
''/etc/default/isc-dhcp-server'' :
<file>
INTERFACES="eth0"
</file>

=== SuSE ===
''/etc/sysconfig/dhcpd'':
<file>
DHCPD_INTERFACE="eth0"
</file>

=== CentOS (bis 6) ===
''/etc/sysconfig/dhcpd'' :
<file>
# Command line options here
DHCPDARGS="eth0"
</file>

===== Testen =====
=== Debian, CentOS 5.3 ===
  dhcpd -t

=== SuSE ===
  rcdhcpd check-syntax

===== starten =====
=== openSuSE (ab 12.1) ===
  service dhcpd start
  chkconfig dhcpd on
=== debian (ab 6.0) ===
  service isc-dhcp-server restart
=== centos (ab 7) ===
  service dhcpd start
===== Client testen =====
Optional: Interface mit passender Mac-Adresse anlegen: [[admin_grundlagen:macvlan]]

DHCP Anfrage ohne Änderung:
=== Debian (ab 6.0) Ubuntu (18.04) ===
  dhclient -d -sf /bin/true eth0
oder
  dhclient -d -sf /usr/bin/env eth0

Unter Ubuntu 18.04 läuft dhclient in einem [[AppArmor]]-Käfig (confinement) und kann daher ''/bin/true'' und ''/usr/bin/env'' nicht ausführen. [[AppArmor|Lösung]]

=== openSuSE (12.3) ===
  dhcpcd --test eth0

=== openSuSE (ab 42.1) ===
  /usr/lib/wicked/bin/wickedd-dhcp4 --test eth0

====== IP-Adress-Pool ======
<file txt /etc/dhcp/dhcpd.conf>
subnet 192.168.227.0 netmask 255.255.255.0 {
  range 192.168.227.50 192.168.227.69;
  …
}
</file>
  dhcpd -t
  service isc-dhcp-server restart
  dhclient -d -sf /bin/true eth0
  dhcp-lease-list

====== Clientseitiges DNS über DHCP konfigurieren ======
<file txt /etc/dhcp/dhcpd.conf>
option domain-name "z03.example.org";
option domain-name-servers 192.168.202.13;
option domain-search "linuxhotel.de", "z03.example.org";
</file>

====== DHCP Client ======
===== DHCP Server Optionen überschreiben =====
Beispiel: eigene DNS-Informationen in die ''resolv.conf'' eintragen
<file txt /etc/dhcp/dhclient.conf>
supersede domain-name "z03.test";
supersede domain-name-servers 192.168.203.101;
</file>
====== Tools ======
  * [[ http://www.webmin.com | Webmin - incl. DHCP und DNS Modul ]] ( in Debian Sarge enthalten, in Etch nicht mehr )
  * [[ http://osuosl.org/projects/maintain/ |  Maintain - web based management tool for DNS and DHCP ]]

====== OMAPI / omshell ======
Ist eine Möglichkeit einen laufenden DHCP-Server ohne Neustart zu steuern ( leases, etc. ). 



====== DHCP Failover ======
Debian 5.0

( noch nicht getestet )

  mv /etc/dhcp3/dhcpd.conf /etc/dhcp3/dhcpd.common.conf
  scp /etc/dhcp3/dhcpd.common.conf notebook25.linuxhotel.de:/etc/dhcp3/dhcpd.common.conf

===== dhcpd.common.conf =====
''/etc/dhcp3/dhcpd.common.conf'' : 
<file>
subnet 192.168.1.0 netmask 255.255.255.0 {
  pool {
    failover peer "dhcp-failover";
    range 192.168.1.100 192.168.1.189;
  }
  option domain-name "linuxhotel.de";
  option domain-name-servers 192.168.1.4, 192.168.1.6;
  option routers 192.168.1.1;
  option broadcast-address 192.168.1.255;
}
</file>

===== Primary =====
''/etc/dhcp3/dhcpd.conf'' : 
<file>
failover peer "dhcp-failover" {
  primary ; # declare this to be the primary server
  address notebook20.linuxhotel.de;
  port 520;
  peer address notebook25.linuxhotel.de;
  peer port 520;
  max-response-delay 60;
  max-unacked-updates 10;
  load balance max seconds 3;
  mclt 1800;
  split 128;
}

include "/etc/dhcp3/dhcpd.common.conf";
</file>
  /etc/init.d/dhcp3-server restart

===== Secondary =====
  /etc/init.d/dhcp3-server stop
''/etc/dhcp3/dhcpd.conf'' : 
<file>
failover peer "dhcp-failover" {
  secondary;
  address notebook25.linuxhotel.de;
  port 520;
  peer address notebook20.linuxhotel.de;
  peer port 520;
  max-response-delay 60;
  max-unacked-updates 10;
  load balance max seconds 3;
}

include "/etc/dhcp3/dhcpd.common.conf";
</file>
  rm /var/lib/dhcp3/dhcpd.leases~
  > /var/lib/dhcp3/dhcpd.leases
  /etc/init.d/dhcp3-server start
Sekunden entsprechend mclt Eintrag warten ...

===== Primary oder Secondary syncronisieren =====
z.B. nach ''Got POOLREQ, answering negatively!  Peer may be out of leases or database inconsistent'' im Log ...
  /etc/init.d/dhcp3-server stop
  rm /var/lib/dhcp3/dhcpd.leases~
  > /var/lib/dhcp3/dhcpd.leases
  /etc/init.d/dhcp3-server start
Sekunden entsprechend mclt Eintrag warten ...